The general aims of this program are to increase our understanding of the maturation of renal function during development, to explore the relationship between developmental renal physiology and disease processes, and to study the natural history and optimal therapy of kidney disease in children. Animal experiments are used in order to define the morphological maturation of the glomerular capillary; the relationship between age and functional adaptation to renal parenchymal loss; and the developmental changes in tubular transport and permeability. The relationship between developmental physiology and disease processes is frequently observed in patients. Volume expansion can be shown to have an adverse effect on the bicarbonate threshold in a child with cystinosis, and the effect of stimulation on organic acid transport can be shown to result in subtherapeutic plasma concentrations of certain antibiotics. Clinical surveys include the effect of a summer recreational experience on the psychosocial development of children requiring hemodialysis; the relationship between low birth weight, low plasma bicarbonate concentrations and growth failure; the incidence and nature of urinary tract abnormalities in children with symptoms of either pyelonephritis or cystitis. In addition, we continue to participate in the various clinical trials of the International Study of Kidney Disease in Children. BIBLIOGRAPHIC REFERENCES: John, E., Goldsmith, D.I., Edelmann, C.M., Jr., and Spitzer, A.: Glomerular capillary volume and surface area during ontogeny. Ped. Res. 11:1084, 1977. Schwartz, G.J., Haycock, G.B., Edelmann, C.M., Jr., and Spitzer, A.: Late metabolic acidosis (LMA):a reassessment. Ped. Res. 11:1114, 1977.